Hydraulic fluid reservoir

ABSTRACT

In order to prevent hydraulic fluid infiltrating out from a hydraulic fluid tank ( 1 ) when a vehicle is in operation, the invention provides for the tank to be compartmentalized by an anti-overflow partition ( 16 ). The anti-overflow partition is made in such a manner as to hold air captive inside the tank in the vicinity of a feed orifice ( 11 ) at a location placed in a top portion of said anti-overflow partition.

The invention relates to a hydraulic fluid tank. In particular, theinvention relates to a hydraulic fluid tank for a vehicle. An object ofthe invention is to limit loss of hydraulic fluid from a hydraulic fluidtank. More precisely, the invention seeks to limit hydraulic fluidlosses when the vehicle is in operation. The invention is moreparticularly intended for the automotive industry, but it can also beapplied to other fields.

In a vehicle, a hydraulic fluid tank serves to feed a hydraulic brakecircuit. Specifically, the hydraulic brake circuit may comprise a mastercylinder connected to braking apparatus including at least one wheel ofthe vehicle. In order to feed the hydraulic brake circuit, the hydraulicfluid tank feeds more particularly a primary chamber and a secondarychamber of said master cylinder. Feeding the primary and secondarychambers of the master cylinder enables primary and secondary pistonsrespectively to compress a volume of hydraulic fluid contained in saidchambers and to move brake pads against at least one disk of a vehiclewheel hub. By compressing a volume of hydraulic fluid, at least onevehicle wheel is impeded and the vehicle can brake.

While the vehicle is in use, it is found that abnormal loss of hydraulicfluid occurs from inside the tank. Such loss of hydraulic fluid requiresa vehicle driver to verify regularly that the level of hydraulic brakefluid inside the tank is sufficient. The level of hydraulic brake fluidis sufficient so long as there is enough hydraulic fluid inside the tankto ensure that the hydraulic brake circuit will operate. The level ofhydraulic fluid therefore needs to be verified by a vehicle user bycomparing the level of hydraulic fluid with a mark situated on a wall ofthe tank, for example. It is tedious that driver safety needs to beensured by regularly verifying the level of hydraulic fluid in the tank,and adding fluid, when necessary. Regularly adding hydraulic fluid tothe tank can also become expensive for the user of the vehicle.

Unfortunately, while the vehicle is in use, the volume of hydraulicfluid inside the tank can be caused to move. More particularly, thehydraulic fluid is caused to move suddenly in a direction of vehicleadvance or in an opposite direction whenever the vehicle decelerates oraccelerates suddenly. The hydraulic fluid can also move sidewaysrelative to the travel direction of the vehicle, for example when thevehicle is making a turn. The tank may also take up a sloping positionrelative to the level of hydraulic fluid in the tank when the vehicle isrunning on a sloping road.

By moving inside the tank, the volume of hydraulic fluid can be causedto cover a tank feed orifice. The hydraulic fluid tank has an orificefor feeding it with hydraulic fluid that is closed by means of astopper. This stopper covers the feed orifice and is usually screwedinto place. When the fluid occupies the feed orifice, hydraulic fluidcan escape from the tank by infiltrating between a thread on the feedorifice and a thread on the stopper. The fluid can also escape from thetank via an air vent made in the stopper. The air vent constitutes asmall hole allowing air to enter into the tank. Air needs to be admittedin order to make it easier to feed the hydraulic circuit with hydraulicfluid.

In order to prevent fluid escaping from the tank, it is possible toincrease the volume of the tank in a vertical direction relative to thevehicle travel direction so that the surface level of the volume ofhydraulic fluid inside the tank practically never reaches the feedorifice of the tank while the vehicle is in use. However, increasing thevolume of such a tank increases the space it occupies under a vehiclehood. In addition, increasing the volume of the tank does not completelyprevent fluid from escaping from the tank.

To solve this problem of fluid escaping from the tank, the inventionprovides for the tank to be compartmentalized by means of at least oneanti-overflow partition. This anti-overflow partition forms an opencompartment inside the tank around and close to the feed orifice of thetank. This anti-overflow partition surrounds the feed orifice at leastin part so that when the tank tilts in at least one given direction, afraction of the volume of air contained inside the tank is held captivein the vicinity of the tank feed orifice. Since the air is held captive,it cannot escape to other locations that are higher up inside the tank.As a result, no suction can be established. The tank then operates likea mercury barometer form which mercury does not escape.

The invention thus provides a hydraulic fluid tank comprising:

a ceiling and a bottom; and

a hydraulic fluid feed orifice, which feed orifice is placed in theceiling and opens out to the outside of the tank, the tank beingcharacterized in that an anti-overflow partition is placed inside thetank extending at least from the ceiling and surrounding the feedorifice at least in part.

The invention will be better understood on reading the followingdescription and on examining the accompanying figures. The figures aregiven purely by way of indication without limiting the invention. In thefigures:

FIGS. 1 a to 1 b are section views of a hydraulic fluid tank of theinvention;

FIG. 1 c is a plan view of a hydraulic fluid tank of the invention;

FIGS. 2 a and 2 b are section views of a hydraulic fluid tank; and

FIGS. 3 a and 3 b are plan views of a hydraulic fluid tank constitutinga variant embodiment of the invention.

FIGS. 1 a to 1 c show a hydraulic fluid tank of the invention for avehicle. In FIG. 1 a, the hydraulic fluid tank 1 comprises a ceiling 2,a bottom 3, and a wall 4. The bottom, the ceiling, and the wall definean inside volume 5. In the example of FIG. 1 a, the inside volume 5 isgenerally in the shape of a cube, however it could be spherical inshape. In this example, the wall 4 is made up of four sides 6, 7, 8, and9. These sides are parallel to each other in pairs. In the example, thesides 6 and 8 are parallel to each other. The ceiling 2 and the bottom 3are disposed in mutually parallel planes. The wall 4 connects theceiling 2 to the bottom 3. The hydraulic fluid tank is filled withhydraulic fluid 10. The tank is fed with hydraulic fluid via a feedorifice 11 situated at a location in the ceiling 2. In the example ofFIG. 1 a, the feed orifice is off-center. The feed orifice may also beplaced at some other location on the tank. The feed orifice is closed bya stopper 12 positioned on the feed orifice 11. The stopper is in theform of a screw cap that is secured to the feed orifice 11 by beingscrewed on, but the stopper could be of any other form and it could besecured by any other means. For example the stopper could be secured byresilient engagement or by snap-fastening.

The volume of hydraulic fluid 10 is intended to feed a hydraulic brakecircuit. For example, a hydraulic brake circuit may comprise a mastercylinder and at least one vehicle wheel (not shown). The volume ofhydraulic fluid 10 is intended more particularly to feed a primarychamber and a secondary chamber of a master cylinder (not shown) via afirst pipe 13 and a second pipe 14. In order to make it easier to movethis volume of hydraulic fluid towards the hydraulic brake circuit andin order to make it easier to move this volume of hydraulic fluid in theopposite direction, the stopper 12 is provided with an air vent 15 thatfacilitates displacement of the volume of hydraulic fluid withoutconstraint inside the tank.

According to an essential characteristic of the invention, the tank isprovided with an anti-overflow partition 16 fixed inside the tank. Theanti-overflow partition has a top portion 16.1 and a bottom portion16.2. The top portion is close to the ceiling. The bottom portion isremote from the ceiling. The anti-overflow partition 16 is secured tothe ceiling 2 via its top portion and it surrounds the feed orifice 11at least in part.

In FIG. 1 a, which is a section view of the tank of the invention asseen from above, the anti-overflow partition 16 can be seen to beU-shaped. The anti-overflow partition forms an open compartment 17inside the tank. Because such a compartment is open, the entire tank canbe fed with hydraulic fluid.

In the example of FIG. 1 c, the U-shape comprises a first portion 18, asecond portion 19, and a third portion 20. The first portion 18comprises a plane parallel to the plane defined by two mutually parallelsides of the four sides of the wall 4. In this example, the two sidesparallel to this first portion 18 are the sides 6 and 8. The second andthird portions 19 and 20 are perpendicular to the first portion 18occupying planes parallel to the planes defined by the other two sidesof the tank. In this example, the other two sides are the sides 7 and 8.The anti-overflow partition 16 forms an open compartment 17 inside thetank and defined by the three above-described portions 18, 19, and 20.

In accordance with the invention, the anti-overflow partition 16 ispreferably fixed perpendicularly to the ceiling of the tank. Thisanti-overflow partition could alternatively be fixed obliquely relativeto the ceiling. The anti-overflow partition is preferably fixed to theceiling of the tank. Under such circumstances, the partition extendspart of the way round the orifice. The anti-overflow partition couldalternatively be fixed solely to the ceiling of the tank.

At rest, the hydraulic fluid in the tank is situated at a levelrepresented by a line 21 in FIG. 2 a. At rest, this line 21 occupies aplane parallel to the plane defined by the ceiling 2 and the bottom 3.During acceleration or deceleration of the vehicle, the fluid tends topile up against a side of the wall of the tank and subsequently to moveback into a plane which may be parallel to a plane of the tank at rest.The fluid may also pile up against a side of the tank when the vehicleis traveling along a sloping road.

In order to simulate acceleration or deceleration of the vehicle, thetank may be caused to lean in at least one direction. Causing the tankto lean also serves to simulate the position occupied by such a tankwhen the vehicle is running on a sloping road. A direction whereby thetank is leaning to the left of the drawing is represented by dashed-linearrow 22 in FIGS. 1 a and 2 a.

When the tank is leaning towards the left of the drawing, the tank tiltsaround the hydraulic fluid and the ceiling of the tank can becomepartially covered in hydraulic fluid as shown in FIGS. 1 b and 2 b.

Without the invention, and as shown in FIG. 2 b, the feed orifice 11closed by the stopper of the tank can become immersed in hydraulic fluidwhen the tank leans in direction 22. The level of hydraulic fluid canthen go down from 21 to a level 23. The level 23 is represented bydashed lines in FIG. 2 b. The level of hydraulic fluid goes down becauseit is possible to exchange air and the fluid overlying the feed orifice.By overlying the feed orifice, fluid can infiltrate between the threadof the tank feed orifice 11 and the thread of the stopper 12. The fluidcan also infiltrate through the air vent 15. The tank thus overflows.

With the invention, and as shown in FIG. 1 b, the anti-overflowpartition 16 prevents the fluid from immersing at least the feed orificeand some of the top portion of the anti-overflow partition. When thetank leans in direction 22, the anti-overflow partition 16 defines afirst level 24 and a second level 25. The first level 24 represents thelevel of the fluid outside the open compartment 17. The second level 25is constituted by the level of the fluid inside the open compartment 17formed by the anti-overflow partition 16.

The anti-overflow partition enables air to be held captive in a locationsituated around the feed orifice. The partition thus prevents the feedorifice from being submerged in hydraulic fluid. In this way, theanti-overflow partition 16 of the present invention makes it possible toavoid hydraulic fluid leaking out from the tank, but only in a singledirection 22.

Unfortunately, when the vehicle is in operation, the volume of fluid canmove in at least four directions. The fluid can move in direction 22 andalso in the opposite direction 26. These two directions 22 and 26 maycorrespond to the positions occupied by the vehicle tank when thevehicle is running on a road that slopes up or a road that slopes down.The hydraulic fluid may also be moved in two other opposite directions27 and 28 perpendicular to the travel direction of the vehicle. Thedirections 26, 27, and 28 are represented by dashed-line arrows in FIGS.3 a and 3 b.

In order to avoid losing hydraulic fluid in at least another one of thefour directions 22, 26, 27, and 28, the invention also provides, in avariant shown in FIGS. 3 a and 3 b, an anti-overflow partitioncomprising a first portion 29 extending part of the way round the feedorifice 11, and a second portion 30 extending around the periphery 31 ofthe tank. An anti-overflow partition made in this way establishes an airflow path inside the tank suitable for isolating the feed orifice fromthe remainder of the tank. This path is made in such a manner as toallow the tank to tilt in at least the four above-mentioned directionswithout fluid covering the feed orifice. This anti-overflow partitionlikewise provides an open compartment 32 inside the tank. The term“periphery” 31 of the tank is used to designate an outline formed by thefour sides 6, 7, 8, and 9 of the tank wall 4. This variant presents theadvantage of making it possible to reduce the height of the volume ofsuch a tank, which can be useful in reducing the vertical height of avehicle hood relative to the position occupied by the vehicle on theroad. In this variant, the anti-overflow partition is preferably fixedboth to the ceiling and to the bottom of the tank.

In this variant, the first portion 29 comprises four wall portions 33,34, 35, and 36 extending part of the way round the feed orifice, and thesecond portion 30 comprises four other wall portions 38, 39, 40, and 41.These two portions are interconnected by a wall portion 37.

A first wall portion 33 extends perpendicularly from a location on oneof the four sides of the wall of the tank to a location in the vicinityof the feed orifice. In the example of FIG. 3 a, the wall portion 33extends from the side 9. Thereafter, this wall portion 33 is extendedperpendicularly by a second wall portion 34, itself extended by a thirdwall portion 35 perpendicular to the second wall portion 34 and parallelto the first wall portion 33. This third wall portion 35 is extendedperpendicularly by a fourth wall portion 36. This fourth wall portion 36is shorter than the second wall portion 34. These four wall portions 33,34, 35, and 36 are disposed in such a manner as to extend part of theway round the feed orifice. The fourth wall portion 36 is then extendedperpendicularly by a fifth wall portion 37 parallel to the first wallportion 33 but not extending as far as the side 9 where the first wallportion 33 is engaged. This fifth wall portion 37 interconnects theportions 29 and 30 of the partition. Thereafter a sixth wall portion 38extends the fifth wall portion 37 perpendicularly. A seventh wallportion 39 extends the sixth wall portion 38 perpendicularly. Thisseventh wall portion 39 is extended perpendicularly by an eighth wallportion 40. The eighth wall portion is itself extended by a ninth wallportion 41. The ninth wall portion 41 does not meet any of the foursides of the tank wall. The sixth, seventh, eighth, and ninth wallportions are disposed in such a manner as to extend around the periphery31 of the tank.

When the tank is caused to lean in direction 26 in FIG. 3 a, theanti-overflow partition serves to hold air captive between the second,third, and fourth wall portions 34, 35, and 36. When the tank is causedto lean in direction 27, the anti-overflow partition serves to hold aircaptive between the first, third, and fourth wall portions 33, 35, and36. If the third wall portion 35 were extended by a wall portion 35.1 soas to meet the sixth wall portion 38 directly instead of going via thefourth wall portion 36, then the feed orifice would become immersed inhydraulic fluid in direction 26. When the tank is caused to lean indirection 28, the anti-overflow partition enables air to be held captivebetween the first, second, and third wall portions 33, 34, and 35.

Other anti-overflow partitions (not shown) of a shape other than thatdescribed above could also be implemented. Such anti-overflow partitionscan also serve to establish an air flow path inside the tank in such amanner as to isolate the feed orifice 11 from the remainder of the tank.In particular, another anti-overflow partition can be made in such amanner as to be spirally-shaped. With such a shape, the anti-overflowpartition can extend part of the way round the feed orifice in such amanner that the anti-overflow partition extends further and further fromthe feed orifice 11 going towards the periphery 31 of the tank. Ananti-overflow partition made in this way can approach the periphery ofthe tank following a circular path or following a rectangular path.

In order to strengthen such a tank and make it better able to withstandthe high pressure that can occur inside the tank, it is possible toprovide at least one stiffening rib 44 as shown in FIG. 3 b. In thisexample, the tank may have a plurality of stiffening ribs 44. Thesestiffening ribs are fixed perpendicularly to at least one of the foursides of the wall 4. These stiffening ribs stiffen the tank. Stiffeningthe tank can be important because the tank must be capable ofwithstanding the high pressures that can occur inside the tank while itis being filled on a motor vehicle assembly line.

In another variant, it is possible to reinforce the rigidity of the tankby causing the anti-overflow partition to be corrugated 43, at least inpart (FIG. 3 b). In the example of FIG. 3 b, a series of corrugationscan be provided in the portion 30 of the anti-overflow partition. Thisleaves room for a stiffening rib to be placed in register with eachcorrugation.

1. A hydraulic fluid tank (1) comprising: a ceiling (2) and a bottom(3); and a hydraulic fluid feed orifice (11), which feed orifice isplaced in the ceiling and opens out to the outside of the tank, the tankbeing characterized in that an anti-overflow partition (16) is placedinside the tank extending at least from the ceiling and surrounding thefeed orifice at least in part.
 2. The tank according to claim 1,characterized in that the anti-overflow partition is fixedperpendicularly to the ceiling of the tank.
 3. The tank according toclaim 1, characterized in that the anti-overflow partition is U-shaped.4. The tank according to claim 3, characterized in that theanti-overflow partition is fixed to the bottom of the tank.
 5. The tankaccording to claim 3, characterized in that the anti-overflow partitionis fixed solely to the ceiling of the tank.
 6. The tank according toclaim 5, characterized in that the tank includes a wall connecting theceiling to the bottom, which wall is provided with stiffening ribs (44)that are preferably fixed perpendicularly thereto.
 7. The tank accordingto claim 6, characterized in that the anti-overflow partition comprisesa first portion (29) extending part of the way around the feed orifice,and a second portion (30) extending around a periphery (31) of the tank.8. The tank according to claim 7, characterized in that the secondportion of the anti-overflow partition surrounding the periphery of thetank includes a series of corrugations (43).
 9. The tank according toclaim 8, characterized in that each corrugation in the second portion ofthe anti-overflow partition is positioned in such a manner as to beplaced in register with a stiffening rib (44).